Reflection-dominated X-ray spectra of narrow-line Seyfert 1 galaxies: Mrk 478 and EXO 1346.2+2645

Multi-epoch XMM-Newton spectra of the two narrow-line Seyfert 1 (NLS1), Mrk 478 and EXO 1346.2+2645, are presented. The data were fitted with different models, including the relativistically blurred reflection model REFLIONX, which was found to give a good description of both spectra in all epochs. The two sources are reflection dominated with the illuminating continuum hidden from view. This can be explained in terms of either a corrugated disc or strong gravitational light bending effects. The emission from these two sources comes from a very small region (a few gravitational radii), very close to a rapidly spinning black hole. Spectral variability analysis shows that both sources have constant rms spectra, and constant hardness ratios in all epochs, in agreement with a single spectral component. The constancy spectrum between high and low states rules out alternative models such as partial covering.